The present invention relates to a method of determining the presence of an object and the type of object on the seat of a passenger vehicle, and a method of determining the deployment of a safety device, particularly airbag deployment.
For controlling the winding of the seat belt or deployment of the airbag, it is inevitable to determine whether or not the seat of the passenger vehicle is vacant, and if not, whether the object present on the seat is a child, an adult, a child seat, or a child seat with a child sitting thereon.
Conventionally, such determination has been made by the output values from the seat weighing instrument mounted to the seat. In other words, when the weight of the seat is below the prescribed value, it is determined that the seat is vacant, and when the value is within a prescribed range, it is determined that a child is sitting or a child seat is mounted on the seat, and when the value is over a prescribed value, it is determined that an adult is sitting on the seat.
Concerning deployment control of the airbag, a no-deployment mode (mode that the airbag is not deployed in case of collision) is selected when it is determined that the seat is vacant; a no-deployment mode or low-deployment mode (mode that the airbag is deployed at a low speed or at low pressure in case of a collision) is selected when it is determined that a child or a child seat is present on the seat; the normal mode is selected when it is determined that an adult is present on the seat. Of course, this method selects the deployment mode of the airbag directly according to the output of the seat weighing instrument, without determining what type of object is on the seat.
However, a method of determining the object on the seat only by the output of the seat weighing instrument as conventionally employed may lead to an inaccurate determination. For example, when the weight of the child seat is heavy or when the child seat is strongly restrained to the seat by a seat belt and a child is sitting on the child seat, the total weight may exceed the value by which the seat is determined to have an adult on the seat. In such a case, the airbag may deploy quickly in the normal mode
With such circumstances, it is an object of the present invention to provide a method of determining the presence and the type of object on the seat accurately and a method of determining the deployment mode of the airbag accurately.
The first embodiment of the invention is a method of determining the presence and the type of object on the seat of the passenger vehicle, including determining whether the seat is vacant, and determining whether the object present on the seat is a child seat, a child, or an adult by the combination of the outputs from the seat weight sensor and a living body proximity sensor.
In this embodiment, the vacancy of the seat or the type of on-board object is determined not only by the seat weight sensor but also by a living body proximity sensor. The living body proximity sensor is affected by the electrostatic capacitance or the electric conductivity of the living body and produces output according to the extent of proximity. (Other types of living body proximity sensors can be envisioned by those of skill in this art.) Because the vacancy of the seat and the type of on-board object are determined by the combination of outputs from the two types of sensors, a more accurate determination can be performed in comparison with the conventional method.
The second embodiment of the invention is the first embodiment, characterized in that:
(a) when the seat weight is below the prescribed value w1, it is determined that the seat is vacant; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output value of the living body proximity sensor shows that the living body is in the proximity thereof, it is determined that a child is present on the seat when the seat weight is below a prescribed value w2 (w1 less than w2), and an adult is present on the seat when the seat weight is equal to w2 or above,
(b2) when the output value of the living body proximity sensor does not show that a living body is in the proximity thereof, it is determined that a child seat is present on the seat.
In this embodiment, the output of the seat weight is examined first and then it is determined that the seat is vacant when the seat weight is below the prescribed value w1, and that something is on the seat when the seat weight is equal to the prescribed value w1 or above. When the seat weight is equal to the prescribed value or above, the type of on-board object has to be determined. At first, the living body proximity sensor is utilized to determine whether a living body is indicated. A threshold value of the output of the living body proximity sensor is set and the output of the sensor is determined to be equal to, above, or below a threshold value.
When the output of the living body proximity sensor indicates that a living body is in its proximity, a human being has been determined as presently sitting directly on the seat. The next step is to determine whether an adult or child is sitting there. A child is sitting on the seat when the seat weight is below a prescribed value w2 (w1 less than w2), and that an adult is sitting on the seat when the seat weight is equal to or above as the prescribed value w2.
When the output of the living body proximity sensor does not indicate the presence of a living body, it is determined that a human being is not sitting on the seat but that a child seat is mounted thereon (including the case where a child is sitting on the child seat).
The third embodiment of the invention is the first embodiment characterized in that:
(a) when the seat weight is below the prescribed value w1, it is determined that the seat is vacant; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output value of the living body proximity sensor shows that the living body is in the proximity thereof, it is determined that a child is present on the seat when the seat weight is below a prescribed value w2 (w1 less than w2), and an adult is present on the seat when the seat weight is w2 or above, or
(b2) when the output value of the living body proximity sensor does not show that the living body is in the proximity thereof, it is determined that a child seat is present on the seat when the seat weight is below a prescribed value w3 (w1 less than w3), and that an adult is present on the seat or the sensor is out of order when the seat weight is equal to w3 or above.
In this embodiment, the output of the seat weight is examined first, and then it is determined that the seat is vacant when the seat weight is below the prescribed value w1 and that something is on the seat when the seat weight is equal to or above the prescribed value w1. When the seat weight is equal to the prescribed value or above, the type of on-board object has to be determined. At first, a living body proximity sensor is utilized to determine whether a living body is indicated. A threshold value of the output of the living body proximity sensor is set and the output of the sensor is determined to be equal to, above, or below the threshold value.
When the output of the living body proximity sensor indicates that a living body is in its proximity, a human being has been determined as presently sitting directly on the seat. The next step is to determine whether an adult or child is sitting there. A child is sitting on the seat when the seat weight is below a prescribed value w2 (w1 less than w2) and that an adult is sitting on the seat when the seat weight is equal to or above the prescribed value w2.
When the output of the living body proximity sensor does not indicate the presence of a living body, it is determined that a human being is not sitting on the seat but that a child seat is mounted thereon (including the case where a child is sitting on the child seat), or the sensor is out of order. When the seat weight is below the prescribed value w3 (w1 less than w3), it is determined that the child seat is mounted thereon (including the case where a child is sitting on the child seat), and when it is equal to or above w3, it is determined that the adult is sitting on the seat or the sensor is out of order. When the seat weight is equal to or above w3, the outputs from the seat weighing instrument and from the living body proximity sensor are not matched. In the case where it is safer to determine that an adult is sitting on the seat to exercise various controls, it is adapted to determine that an adult is sitting on the seat. Where exercising controls under such a determination is dangerous, it is adapted to give an alarm indicating that the sensor is out of order. The values of w2 and w3 are normally different, but they may be the same value in some cases.
The fourth embodiment of the invention is the first embodiment, characterized in that:
(a) when the seat weight is equal to or below the prescribed value w1, it is determined that the seat is vacant; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output value p of the living body proximity sensor is smaller than the function f(w) determined by the seat weight w1, it is determined that a child is present on the seat when the seat weight is below the prescribed value w2 (w1 less than w2), and an adult is present on the seat when it is equal to or above w2,
(b2) when the output value of the living body proximity sensor is equal to or above the function f(w) determined by the seat weight w, it is determined that a child seat is present on the seat, and that an adult is sitting on the seat or the sensor is out of order when the value is equal to or above w3, where the output p of the living body proximity sensor becomes smaller when the living body is in the proximity thereof.
In this embodiment, the output of the seat weight is examined first and then it is determined that the seat is vacant when the seat weight is below the prescribed value w1, and that something is on the seat when the seat weight is equal to or above the prescribed value w1. When the seat weight is equal to or above the prescribed value, the type of on-board object has to be determined. A living body proximity sensor is used and a threshold value of the output of the living body proximity sensor is set to the function f(w) that is determined by the output w of the seat weight sensor, in contrast to the second embodiment and the third embodiment.
The reason is that the output of the living body proximity sensor may differ according to the size of the living body (human being) sitting on the seat. In other words, when an adult whose weight and the sitting area is larger than those of a child is sitting on the seat, the output of the living body proximity sensor is shifted to the side of xe2x80x9cproximityxe2x80x9d in comparison with the case where a small child is sitting on the seat.
Therefore, considering that the sitting area is large when the weight is heavy, these values are represented by the seat weight, and the threshold value is approximated by the function f(w) defined by the output w1 of the seat weight sensor. Assuming that the larger the weight and the sitting area are, the smaller the output value of the living body proximity sensor becomes, f(w) is a monotone decreasing function. However, when the actual output of the living body proximity sensor is smaller than the threshold value f(w), it is determined that a human being is sitting on the seat. When the seat weight is below the prescribed value w2 (w1 less than w2), it is determined that a child is sitting on the seat. When the seat weight is equal to or above w2, it is determined that an adult is sitting on the seat.
When the output of the living body proximity sensor is equal to or above the threshold value f(w) determined by the seat weight w1, it is determined that there is no human being sitting directly on the seat, but that a child seat is mounted on the seat (including the case where a child is sitting on the child seat) or the sensor is out of order. Therefore, when the seat weight is below the prescribed value w3 (w1 less than w3), it is determined that a child seat is mounted on the seat (including the case where a child is sitting on the child seat). When the seat weight is equal to or above w3, it is determined that an adult is sitting on the seat or the sensor is out of order. When the seat weight is equal to or above w3, the outputs from the seat weighing instrument and from the living body proximity sensor are not matched. In the case where it is safer to determine that an adult sitting on the seat to exercise various controls, it is adapted to determine that an adult is sitting on the seat, and where exercising controls under such a determination is dangerous, it is adapted to give an alarm indicating that the sensor is out of order. The values of w2 and w3 are normally different, but it may be the same value in some cases.
The fifth embodiment of the invention is a method of determining the airbag deployment mode, characterized in that the deployment mode is determined by the combination of the output from the seat weight sensor and that from the living body proximity sensor mounted on the seat.
In this embodiment, the living body proximity sensor as well as the seat weight sensor is used for determining the airbag deployment mode. The living body proximity sensor is, when the living body is in the proximity thereof, affected by the electrostatic capacitance or the electric conductivity of the living body and produces output according to the extent of proximity. In this embodiment, because determination of the deployment mode of the airbag is by the combination of outputs from two types of sensors, accurate determination can be performed in comparison with the conventional method.
The sixth embodiment of the invention is the fifth embodiment characterized in that:
(a) when the seat weight is below the prescribed value w1, the airbag is not deployed; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output of the living body proximity sensor shows that the living body is in the proximity thereof, the no-deployment mode or the low deployment mode is selected when the seat weight is below the prescribed value w2 (w1 less than w2), and the normal deployment mode is selected when the seat weight is equal to or above w2, and
(b2) when the output of the living body proximity sensor does not show that living body is in the proximity thereof, the no-deployment mode or low-deployment mode is selected.
The seventh embodiment of the invention is the fifth embodiment, characterized in that:
(a) when the seat weight is below the prescribed value w1, the no-deployment mode is selected; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output of the living body proximity sensor shows that the living body is in the proximity thereof, the no-deployment mode or the low deployment mode is selected when the seat weight is below the prescribed value w2 (w1 less than w2), and the normal deployment mode is selected when the seat weight is equal to or above w2,
(b2) when the output of the living body proximity sensor does not show that living body is in the proximity thereof, the no-deployment mode or low deployment mode is selected when the seat weight is below the prescribed value w3 (w1 less than w3), and the normal deployment mode is selected when the seat weight value is equal to or above w3.
The eighth embodiment of the invention is the fifth embodiment, characterized in that:
(a) when the seat weight is below the prescribed value w1, the no-deployment mode is selected; and
(b) when the seat weight is equal to or above the prescribed value w1; and
(b1) when the output p of the living body proximity sensor is smaller than the function f(w) determined by the seat weight w, the no-deployment mode or the low deployment mode is selected when the seat weight is below the prescribed value w2 (w1 less than w2), and the normal deployment mode is selected when the seat weight is equal to or above w2,
(b2) when the output from the living body proximity sensor is equal to or above the function f(w) that is determined by the seat weight w1, the no-deployment mode or the low deployment mode is selected when the seat weight w1 is smaller than w3 (w1  less than w3), and the normal deployment mode when the seat weight is equal to or above w3, where the output of the living body proximity sensor p becomes smaller when the living body is in the proximity thereof.
In the sixth embodiment of the eighth embodiment, the airbag is selected to be the no-deployment mode when the seat is vacant, and the no-deployment mode or the low-deployment is selected when a child is sitting on the seat or when a child seat is mounted on the seat, and the normal-deployment mode is selected when an adult is sitting on the seat or the sensor is out of order. To the determination thereof, a logic described in the second embodiment and the third embodiment is applied.